题目内容：

这是定语从句吗,为什么可以省略which?
And each of them wrote a paper relating to athletics and justice in the universities.
为什么paper后面可以省略which,不是说which在定语从句忠做主语不能省略吗?这样不是有两个动词wrote 和 relating 还是说relating 不是动词?英文很烂求指教